AA MAXs can 100-0 an ESF in rare circumstances, but generally you just fire at stuff that's close enough that you can actually hit it. If there's more than one AA, or they're hovering, or they do a second pass without repairing, then you can kill them.

Also, if a lib is directly above you, make sure you can easily take cover. Their belly gun will kill you before you can do much to them if they see you.